The present disclosure relates to lamps, and more specifically to lighting circuits used in vehicles.
Modern vehicle lamps, particular those mounted on the vehicle exterior which utilize light emitting diodes (LEDs) as the light source, are typically composed of multiple light emitting elements or LEDs in a single housing. It is important for the operator to be made aware if one or more LEDs in a lamp have failed, so that corrective measures can be taken to replace the faulty lamp or associated components. However, if a single or even multiple individual LEDs in a lamp malfunctions, the overall drop in current or voltage may not be enough to trigger traditional lamp failure warning circuitry and also may not be noticeable during visual inspection. Furthermore, if the LEDs are being driven by a constant current source, failure of one LED may cause excess current to be directed to the remaining LEDs, potentially causing damage or further failures.
One option for detecting LED failures in such vehicle lamps is to include microprocessors in the lamp housing or lighting circuit which have been programmed and connected to sense the current through the individual LEDs. However, this approach is often cost prohibitive due to the extensive software development and testing operations that are typically required. There are also some LED driver integrated circuits in the market which provide an outage detection feature, although these devices are typically confined to a single lighting arrangement with respect to the number of parallel LED branches that can be monitored or the number of failed LED branches that will trigger an outage indicator signal to be produced.
Thus, there is a need for improvement in this field.